This section provides background information related to the present disclosure which is not necessarily prior art.
Generally, a fuel cell (polymer electrolyte membrane fuel cell) is structured of a cell stack that overlays multiple single cells. In this regard, a single cell is a structure constituted of an electrolyte membrane, a catalyst layer disposed to envelop the electrolyte membrane, and a gas diffusion layer disposed to envelop both of the former. In addition, the electrodes are structured by the catalyst layer and the gas diffusion layer, with the surface facing the electrolyte membrane being the anode, and the other facing surface being the cathode. Fuel that includes hydrogen is flowed over the anode side, and an oxidizing agent that includes oxygen is flowed over the cathode side, generating electricity by the reaction at the catalyst layer.
The following section describes a fuel cell according to a former technology example by referencing FIGS. 7˜12. Furthermore, with this former technology example, there is provided a reaction membrane structured by the integration of an electrolyte membrane and a catalyst layer disposed on each side of the electrolyte membrane. FIG. 7 is a plane view drawing of a portion of the single cell structure in the fuel cell according to the former technology example. FIG. 8 is a typical cross section drawing (a cross section of line BB in FIG. 7) of the single cell structural component in the fuel cell according to the former technology example. FIG. 9 is a typical cross section drawing in which there has been performed component development of the single cell structural component in the fuel cell according to the former technology example. FIG. 10 is a plane view drawing of a portion of the reaction membrane according to the former technology example. FIG. 11 is a plane view drawing of a portion of the gasket that has integrally provided the gas diffusion layer according to the former technology example. FIG. 12 is a plane view drawing of a portion of the separator according to the former technology example.
As described above, the fuel cell is a structure in which a single cell provides multiple overlaid separators. The following explanation describes only the single cell structural component that is structured by the members that structure the single cell.
Single cell structural component 200 is structured by reaction membrane 210, gasket 220 that provides anode side gas diffusion layer 221a and cathode side gas diffusion layer 221b disposed so as to envelop reaction membrane 210, and a pair of separator 230 disposed so as to envelop all of the former.
Additionally, at single cell structural component 200, there is disposed fuel manifold R10 for supplying fuel to anode side gas diffusion layer 221a, and disposed oxidizing agent manifold R20 for supplying an oxidizing agent to cathode side gas diffusion layer 221b. Moreover, at single cell structural component 200, there is also disposed cooling water manifold R30 as the flow route for cooling water (refer to FIG. 7).
The following section describes gasket 220 by referencing FIG. 11 in particular. Gasket 220 is structured by anode side gas diffusion layer 221a, cathode side gas diffusion layer 221b, and elastic body 225 disposed integrally with the former. Additionally, at elastic body 225, there are formed first passage hole 222 that forms a part of fuel manifold R10, second passage hole 223 that forms a part of oxidizing agent manifold R20, and third passage hole 224 that forms a part of cooling water manifold R30. Moreover, at elastic body 225, there is disposed protrusion S that tightly adheres to such as separator 230. In FIGS. 7 and 11, the position of this disposed protrusion S is shown by dotted line SL.
The following section describes separator 230 by referencing FIG. 12 in particular. FIG. 12 (a) shows the surface of the anode side, and FIG. 12 (b) shows the surface of the cathode side. At separator 230, there are formed first passage hole 232 that forms a part of fuel manifold R10, second passage hole 233 that forms a part of oxidizing agent manifold R20, and third passage hole 234 that forms a part of cooling water manifold R30. That being the case, at the surface of the anode side of separator 230, there is formed recessed section 235a adjacent to first passage hole 232, and there are formed, so as to pass through recessed section 235a, a plurality of channel 231a that forms a flow route between first passage hole 232 and anode side gas diffusion layer 221a. Moreover, at the surface of the cathode side of separator 230, there is formed recessed section 235b adjacent to second passage hole 233, and there are formed, so as to pass through recessed section 235b, a plurality of channel 231b that forms a flow route between second passage hole 233 and cathode side gas diffusion layer 221b. 
That being the case, into recessed section 235a and recessed section 235b, there are installed respective occurrences of plate member (bridge) 240, in such a way as to cross over the plurality of channel 231a and of 231b. 
With the above described structure, fuel from fuel manifold R10 (first passage holes 222 and 232) is sent to anode side gas diffusion layer 221a, and oxidizing agent from oxidizing agent manifold R20 (second passage holes 223 and 233) is sent to cathode side gas diffusion layer 221b. In this way, the hydrogen contained in the fuel and the oxidizing agent react, resulting in electricity.
In this instance, protrusion S disposed on elastic body 225 is disposed for the purpose of isolating the companion regions to which respectively flow fuel, oxidizing agent, and cooling water. To be specific, protrusion S is established to form tightly sealed regions, and most of its components manifest the function of a seal protrusion. Basically, it is disposed to respectively encompass anode side gas diffusion layer 221a, cathode side gas diffusion layer 221b, and the passage holes that form a part of each manifold.
As described above, with this former technology example, a plurality of channels 231a and of 231b are formed in separator 230 in order to send fuel to anode side gas diffusion layer 221a and oxidizing agent to cathode side gas diffusion layer 221b. That being the case, plate member 240 is attached so as to cross over the plurality of 231a and of 231b, and protrusion S is made to tightly adhere in a way that crosses over plate member 240 (FIG. 7). The following section explains the reason for adopting this type of structure. Moreover, because the anode side and cathode side are of an identical structure, the following explanation uses the cathode side as an example.
The oxidizing agent that flows through oxidizing agent manifold R20 is sent to cathode side gas diffusion layer 221b, as described above. Accordingly, with the former technology, it was sufficient to utilize a space to connect the spatial region of oxidizing agent manifold R20 to the spatial region that faces cathode side gas diffusion layer 221b, and as long as there is assured a flow route for the oxidizing agent, then the channel, plate member, and protrusion described above are not necessary. On the other hand, in order that oxidizing agent flowing from oxidizing agent manifold R20 not leak to the anode side, at the anode side, the protrusion that encompasses oxidizing agent manifold R20 is necessary. Therefore, in order to cause more reliable adhesion of protrusion S1 to separator 230 and thereby manifest seal performance, it is necessary to support protrusion S1 from the opposite side. On that point, with the former technology example, in order to support the opposite site of protrusion S1, there is disposed a protrusion (protrusion S2 in FIG. 8) tightly adhered against separator 230 at an identical position directly behind protrusion S1. However, if there is only disposing of this protrusion S2, there would result a blockage between the spatial region of oxidizing agent manifold R20 and the spatial region that faces cathode side gas diffusion layer 221b. Consequently, after having established the plurality of channel 231b that become flow routes for the oxidizing agent, there is established plate member 240 in order that protrusion S2 will not be pushed into within channel 231b. 
As described above, of the occurrences of protrusion S disposed on elastic body 225, those components that cross over the section between the manifold and the gas diffusion layer to which gas is sent from the manifold are not disposed for the purpose of forming a tightly sealed region by their presence, but are disposed for supporting the protrusion (seal protrusion) at the opposite side.
That being the case, in order to manifest stable seal performance, during the condition in which plate member 240 has been attached to recessed sections 235a and 235b of separator 230, it is ideal for there not to be generated a difference in dimension to the surface of separator 230.
However, to make favorable the installability, a clearance is established between the inner side surface of recessed sections 235a and 235b and the outer side surface of plate member 240. As a consequence, for example, as shown by section X of FIG. 8, a gap is generated between the inner side surface of recessed sections 235a and 235b and the outer side surface of plate member 240. Additionally, a difference in dimension may also be generated at the section shown by X1 of FIG. 7, due to the impact of a dimensional aberration for the depth of recessed sections 235a and 235b and the thickness of plate member 240. Furthermore, reaction membrane 210 is encompassed by gasket 220 having a surface area larger than reaction membrane 210, and therefore a difference in dimension may also be generated at the edge vicinity of reaction membrane 210 (section X2 of FIG. 7, for example).
The above described gaps and differences of dimension may adversely impact seal performance.
Furthermore, reaction membrane 210 that structures the single cell structural component shown in FIGS. 7-9 is structured so that the surface area is smaller than that of separator 230, as shown in FIG. 10 (a). In relation to this, when using a reaction membrane that is of identical size to that of separator 230, such as reaction membrane 210X shown in FIG. 10 (b), there is to a degree enabled the elimination of the problem of reduced seal performance due to the existence of a difference in dimension. However, the membrane is in general exceptionally expensive, and therefore it is desirable to use that which has as small an area as possible, by disposing the membrane only in the vicinity of the reaction region for the hydrogen and oxidizing agent.